Socrates' predecessors: philosophy and the natural order -- Socrates and the Sophists: the problems of truth and goodness -- Plato -- Aristotle -- Classical philosophy after Aristotle -- St. Augustine's Christian philosophy -- Philosophy in the Dark Ages: Boethius, pseudo-Dionysius, Erigena -- Early statements of major problems -- The apex of medieval philosophy: the scholastic system of St. Thomas Aquinas -- The Renaissance interlude -- Advocates of the method of science: Bacon and Hobbes -- Rationalism on the continent: Descartes, Spinoza, and Leibniz -- Empiricism in Britain: Locke, Berkeley, and Hume -- Rousseau: a romantic in the age of reason -- Kant: critical mediator between dogmatism and skepticism -- Hegel: absolute idealism -- Schopenhauer: prophet of pessimism -- Comte: the rise of positivism in France -- Utilitarianism of Bentham and Mill -- Pragmatism -- Karl Marx: dialectical materialism -- Nietzsche -- Two twentieth-century metaphysicians: Bergson and Whitehead -- Analytic philosophy -- Existentialism.